Research questions

Mother and healthworker examine child with pneumonia, Kilifi County Hospital, Kenya

PCVIS set out to answer a number of research questions relating to the direct and indirect effects of PCV10, including:

Does PCV10 have an impact on pneumonia in children? 

Pneumonia is the biggest cause of childhood death globally, and pneumococcus bacteria are the most common trigger for the illness. PCVIS has measured incidence of pneumonia before and after introduction of PCV10.

Does PCV10 have an impact on invasive pneumococcal disease (IPD) in children?

A major objective of the study was to monitor changes in IPD before and after introduction of PCV10. Data on admissions with IPD at the paediatric ward of the Kilifi County Hospital are available from 2000 to date. This has allowed the team to accurately report the trend in IPD admission rates over the years before and after introduction of PCV10 and therefore whether the vaccine has had an impact on pneumococcal disease.

What causes pneumonia?

We do not know the cause of over a quarter of all pneumonia. In PCVIS, blood and other samples collected from children admitted to hospital with pneumonia and IPD are used to find what is causing the disease. Researchers can use these samples to identify which strain - or serotype - of the streptococcus pneumoniae bacteria is causing IPD over time and see if the vaccine is working to get rid of the serotypes it targets.

As serotypes of pneumococcal bacteria included in the vaccine start to disappear their space can soon be occupied by other serotypes of pneumococcal bacteria against which the vaccine offers no protection. To be sure that any serotypes replacing the vaccine-types are harmful or not, the PCVIS team will compare samples from healthy children within the KHDSS with those from children admitted in the wards with IPD.

Does childhood PCV10 vaccination protect adults?

Blood and other samples collected from all adults in Kilifi County Hospital diagnosed with pneumonia and meningitis and tested to identify what has caused the illness. If the bacteria Streptococcus pneumoniae is detected, researchers find out which serotype it is and whether it is one targeted by the vaccine, or not. This will show how effective the vaccine has been in preventing non-vaccinated adults from getting IPD caused by the serotypes PCV10 targets – a population level protection known as herd immunity.

Does PCV10 increase adverse reactions?

Safety monitoring after introduction of a new vaccine is paramount. Synflorix®, the PCV10 vaccine introduced in Kenya, does not contain a preservative meaning it cannot be used more than 6 hours after opening. If the more stringent rules for using this vaccine aren’t followed, it could lead to contamination-related adverse events, such as abscesses or severe bacterial infections. Three demographic surveillance sites were involved in this study to investigate and report on adverse events: the KEMRI Centres for Disease Control and Prevention Research and Public Health Collaboration International Emerging Infections Program population-based disease surveillance sites in Kibera and Rarieda Districts, and the KEMRI Centre for Global Health Research Health and Demographic Surveillance System site in Siaya District.